Picocomputer
The next generation of Picocomputer 6502 #137
Replies: 7 comments 5 replies
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I've started building a new Picocomputer that will use Pico2s. I don't want to disturb my existing Picocomputer. I've got all the parts and will report back once it's running. May take a few days, as I'm trying to finish some other projects before I get deep into this one. |
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Looks like the hardware interpolator changed in the RP3250. I can't get the overflow bit to work. This broke affine sprites. I now compute overflow on the CPU which means less fill rate for asprites. I tested @vruumllc's Star Swarms and the examples, none of which are exceeding the new fill rate. If you're good at ARM assembly, please look at the sprite_ablit16_alpha_loop_body implementation and see if you can shave off any cycles. Still need to do the time rewrite. I haven't seen a single glitch with the new gpio timings, which is fantastic since debugging that is a lot of work. |
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Oooo! Sign me up for any help you might want. I've already got a board with 2 pico2s in it, waiting for the day when either I got around to it, or someone else did. I'm super-stoked that you are proceeding with further development. |
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Today I upgraded the all-in-one you sent me. Be sure to notice the Pi Pico 2 audio noise is a lot lower and much less grating. Thanks again for sending it. Hundreds of people have seen it. |
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Cool! I'm so glad people are having fun with it. |
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The pico2 branch has been merged and released. |
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All good news, thanks for the support & development. |
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pico2 are en route, hopefully i can get a pico computer upgraded and get back to playing around with this |
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Built my new Picocomputer 6502 yesterday, and it's working fine. Tried it at clock speeds 0.5, 1, 2, 4, and 8 MHz: all good. I was interested to see a Hackaday post yesterday about a FORTH that's just been ported to the 6502 and fits in just over 1K of memory. I might try porting that to the Picocomputer 6502, getting it to run standalone, without needing a PC attached to act as a terminal, and then add some FORTH words for supporting the Pico's graphics. Not really relevant to the Picocomputer 6502, but it was interesting to see lftkryo's YouTube demo yesterday, showing what a single Pico2 can produce in the way of graphics and sound - all programmed in RISC-V assembly. |
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I have milliForth compiling with changes needed to use the RP6502 UART but it's not working. |
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Actually, it does work, it's just slower than expected. It takes 10 seconds to print hello world. I don't have plans for this. Just wanted to be first to maybe get a shoutout from hackaday. Feel free to take over from here. |
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Wow! 10 seconds? Something must be wrong. |
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Time for some new hardware!
Why is a change needed?
The RP6502-RIA has no free RAM. You can tag individual functions or data to be moved to ROM, but this is tedious and I didn't want to maintain such a beast. There's a lot of time-critical code so it's easy to make a mistake that could result in an intermittent fault.
What's changing?
The 2 Pi Picos are being replaced with 2 Pi Pico 2s. No other hardware changes are planned. The upgrade is expected to take 10 minutes and 10 dollars.
What were the challenges?
The RP2350 has slightly different timings for reading GPIO. Since this project uses PIO at its limit, some of it needed to be rewritten for the new timings. Other PIO sections needed to be retimed. The RP2350 changelog was missing Information about GPIO fabric changes which added unnecessary complexity.
What's left to do?
The real-time-clock in the RP2040 has been replaced with a simple counter in the RP2350. For now, RIA time functions have been disabled. The changes needed seem straightforward, the work just hasn't been done. I think this is the only blocker to making versioned releases.
What about compatibility?
The new hardware fundamentally only adds RAM so the RP6502-RIA can be developed further. Application binaries written for Pi Pico 1 systems will run on the Pi Pico 2. Future support for the Pi Pico 1 is being dropped.
Anything else?
The install process for building Pi Pico firmware has been greatly simplified. I migrated the build system to use the Pi Pico VSCode Extension which automatically handles installing the compiler toolchain.
What help is needed?
Mostly testing. Especially with different PHI2 values. Please test anything you wrote and try some new things. If you're feeling ambitious, look into making an RP6502 VSCode Extension or peruse the issue trackers.
Where do I get it?
It's on a branch. I've attached binaries here so you can quickly validate your hardware upgrade. I don't plan on releasing any more binaries until v0.10 is ready.
rp6502_pico2_aplha.zip
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